On the nature of chromophore in pig kidney diamine oxidase.

The nature of the 500-nm chromophore in pig kidney diamine oxidase was investigated by absorption spectroscopy and fluorescence in the presence of various chelating or carbonyl-specific reagents. From the spectroscopic measurements the following conclusions can be drawn. First, the 500-nm absorption band is not due to copper, the reduction of which is not related to the disappearance of this band. Second, phenylhydrazine and cycloserine give rise, upon reaction with the enzyme, to absorptions very similar to those of a pyridoxal enzyme, aspartate aminotransferase. Third, these enzyme derivatives are unexpectedly non-fluorescent. Copper removal, obtained after prolonged incubation of cycloserine-treated enzyme in the presence of reducing and chelating agents, leads to a fluorescence similar to that of cycloserine-aspartate transminase. It is proposed that copper is coordinated to the postulated pyridoxal phosphate of diamine oxidase through the pyridine nitrogen.     

The synergism acetylcholine-eserine in the epinephrine induced ventricular automaticity

Heart ventricular strips of the rat in Krebs solution were used to test the synergism acetylcholine-eserine. Ventricular automaticity induced by epinephrine 1 10(-6) is inhibited by acetylcholine (a 50% reduction of the automatism is observed with acetylcholine 1,23 10(-8) while four different concentrations of eserine cause an evident potentiation of the effect of acetylcholine (with eserine a 10(-5) the ED50 of acetylcholine is 2,57 10(-14)). It is concluded that the synergism eserine-acetylcholine is a synergism with potentiation and the acetylcholine introduced in the Krebs solution interacts with receptors different from those activated by the acetylcholine which accumulates when cholinesterase is inhibited by eserine.     

Epidemic management and control through risk-dependent individual contact interventions

Testing, contact tracing, and isolation (TTI) is an epidemic management and control approach that is difficult to implement at scale because it relies on manual tracing of contacts. Exposure notification apps have been developed to digitally scale up TTI by harnessing contact data obtained from mobile devices; however, exposure notification apps provide users only with limited binary information when they have been directly exposed to a known infection source. Here we demonstrate a scalable improvement to TTI and exposure notification apps that uses data assimilation (DA) on a contact network. Network DA exploits diverse sources of health data together with the proximity data from mobile devices that exposure notification apps rely upon. It provides users with continuously assessed individual risks of exposure and infection, which can form the basis for targeting individual contact interventions. Simulations of the early COVID-19 epidemic in New York City are used to establish proof-of-concept. In the simulations, network DA identifies up to a factor 2 more infections than contact tracing when both harness the same contact data and diagnostic test data. This remains true even when only a relatively small fraction of the population uses network DA. When a sufficiently large fraction of the population (≳ 75%) uses network DA and complies with individual contact interventions, targeting contact interventions with network DA reduces deaths by up to a factor 4 relative to TTI. Network DA can be implemented by expanding the computational backend of existing exposure notification apps, thus greatly enhancing their capabilities. Implemented at scale, it has the potential to precisely and effectively control future epidemics while minimizing economic disruption.     

Calcium in the micropylar secretion and receptivity of explanted Crocus ovules to intra- and interspecific pollen

The micropylar secrete of the ovules of Crocus vernus ssp. vernus was analyzed for the Ca⁺² content by atomic absorption, and its capacity to germinate and attract pollen was tested by pollinating explanted ovules, and incubating in absence of culture medium. The results display a Ca⁺² concentration of 28.9 mM in the micropylar secrete. On this secrete both compatible- and incompatible pollen germinates with a mean percentage of 53.7%, and their pollen tubes enter the micropylar canal with percentages of 32.3% to 21.0%. In situ the ovules fail to attract tubes of incompatible pollen. The results are discussed in relation to the ovule receptivity and the guided growth of pollen tubes, substantiating the model of the tropic growth towards increasing calcium concentrations.     

Biomarker of food intake for assessing the consumption of dairy and egg products

Dairy and egg products constitute an important part of Western diets as they represent an excellent source of high-quality proteins, vitamins, minerals and fats. Dairy and egg products are highly diverse and their associations with a range of nutritional and health outcomes are therefore heterogeneous. Such associations are also often weak or debated due to the difficulty in establishing correct assessments of dietary intake. Therefore, in order to better characterize associations between the consumption of these foods and health outcomes, it is important to identify reliable biomarkers of their intake. Biomarkers of food intake (BFIs) provide an accurate measure of intake, which is independent of the memory and sincerity of the subjects as well as of their knowledge about the consumed foods. We have, therefore, conducted a systematic search of the scientific literature to evaluate the current status of potential BFIs for dairy products and BFIs for egg products commonly consumed in Europe. Strikingly, only a limited number of compounds have been reported as markers for the intake of these products and none of them have been sufficiently validated. A series of challenges hinders the identification and validation of BFI for dairy and egg products, in particular, the heterogeneous composition of these foods and the lack of specificity of the markers identified so far. Further studies are, therefore, necessary to validate these compounds and to discover new candidate BFIs. Untargeted metabolomic strategies may allow the identification of novel biomarkers, which, when taken separately or in combination, could be used to assess the intake of dairy and egg products.     

Carrier subunit of plasma membrane transporter is required for oxidative folding of its helper subunit

We study the amino acid transport system b(0,+) as a model for folding, assembly, and early traffic of membrane protein complexes. System b(0,+) is made of two disulfide-linked membrane subunits: the carrier, b(0,+) amino acid transporter (b(0,+)AT), a polytopic protein, and the helper, related to b(0,+) amino acid transporter (rBAT), a type II glycoprotein. rBAT ectodomain mutants display folding/trafficking defects that lead to type I cystinuria. Here we show that, in the presence of b(0,+)AT, three disulfides were formed in the rBAT ectodomain. Disulfides Cys-242-Cys-273 and Cys-571-Cys-666 were essential for biogenesis. Cys-673-Cys-685 was dispensable, but the single mutants C673S, and C685S showed compromised stability and trafficking. Cys-242-Cys-273 likely was the first disulfide to form, and unpaired Cys-242 or Cys-273 disrupted oxidative folding. Strikingly, unassembled rBAT was found as an ensemble of different redox species, mainly monomeric. The ensemble did not change upon inhibition of rBAT degradation. Overall, these results indicated a b(0,+)AT-dependent oxidative folding of the rBAT ectodomain, with the initial and probably cotranslational formation of Cys-242-Cys-273, followed by the oxidation of Cys-571-Cys-666 and Cys-673-Cys-685, that was completed posttranslationally.     

Biosensors and molecular imaging

The increase in the understanding of the physical and functional properties of the biological material, from the cellular level down to single molecules, owes its success to the development of suitable high-sensitivity platforms to image the biomaterial and analyze its response to specific stimuli. Imaging has indeed reached molecular capabilities, thanks to optical or magnetic markers [1], to the atomic force microscopy (AFM) in surface reconstruction [2], and is nearing success in three-dimensional (3-D) reconstruction thanks to X-ray holography [3].     

Multiple effects of paclitaxel are modulated by a high c-myc amplification level

Paclitaxel affects microtubule stability by binding to beta-tubulin, thus leading to cell accumulation in the G(2)/M phase, polyploidization, and apoptosis. Because both cell proliferation and apoptosis could be somehow regulated by the protooncogene c-myc, in this work we have investigated whether the c-myc amplification level could modulate the multiple effects of paclitaxel. To this aim, paclitaxel was administered to SW613-12A1 and -B3 human colon carcinoma cell lines (which are characterized by a high and low c-myc endogenous amplification level, respectively), and to the B3mycC5 cell line, with an enforced exogenous expression of c-myc copies. In this experimental system, we previously demonstrated that a high endogenous/exogenous level of amplification of c-myc enhances serum deprivation- and DNA damage-induced apoptosis. Accordingly, the present results indicate that a high c-myc amplification level potentiates paclitaxel cytotoxicity, confers a multinucleated phenotype, and promotes apoptosis to a great extent, thus suggesting that c-myc expression level is relevant in modulating the cellular responses to paclitaxel. We have recently shown in HeLa cells that the phosphorylated form of c-Myc accumulates in the nucleus, as distinct nucleolar and extranucleolar spots; here, we demonstrated that, after the treatment with paclitaxel, phosphorylated c-Myc undergoes redistribution, becoming diffused in the nucleoplasm.     

Muscle differentiation in a colonial ascidian: organisation, gene expression and evolutionary considerations

Background  

Ascidians are tunicates, the taxon recently proposed as sister group to the vertebrates. They possess a chordate-like swimming larva, which metamorphoses into a sessile adult. Several ascidian species form colonies of clonal individuals by asexual reproduction. During their life cycle, ascidians present three muscle types: striated in larval tail, striated in the heart, and unstriated in the adult body-wall.